In wireless communication systems, a specific frequency band is assigned for the operation of the specific system. In general, the frequency band is divided into a number of frequency channels, and each of the channels only occupies a fraction of the whole band. In a narrow-band communication system, the transmitter and receiver will select one channel for signal transmission. In a frequency-hopping spread spectrum (FHSS) communication system with adaptive frequency hopping (AFH), the system has to first determine the quality of each channel. The major impact to the channel quality is interference. The quality of a channel becomes bad if the frequency range thereof is overlapped with an interference source.
There are various types of interferences. Some typical interferences have bandwidths narrower than that of a channel. Others may have bandwidth that span from several to tens of the channels. Normally, the receiver only detects in a single channel each time, and switches from channel to channel to make a number of detections. Conventionally, the channel quality assessment for a channel is done by collecting the detections of this channel and is independent from the detections of other channels. As the number of channels becomes large, the total time for channel assessment for all channels becomes very long. Referring to Kwang-Cheng Chen, Hung-Kun Chen, and Chi-Chao Chao, Selective Hopping for Hit Avoidance, in IEEE P802.15 Working Group Contribution, IEEE 802.15-01/057r2, March 2001, a method for channel quality assessment is disclosed, wherein the channels are divided into three partitions and each partition is treated as a whole. This method proves much faster for channel assessment, but much of the frequency resolution is unfortunately lost.